In the production of electronic equipment utilizing I/C chips and the testing and use of the I/C chips in electronic circuitry, one common technique is to mount the I/C chip onto a chip carrier by what is sometimes known as "flip-chip" mounting. In such a technique, a ceramic carrier is provided which may be a metalized chip carrier or a multi-layer ceramic chip carrier, with chip mounting pads formed on the surface. The carrier may be used for either permanently mounting the chips, i.e., mounting the chips for ultimate packaging by connecting the carrier to a circuit board, or it may be mounted temporarily or removably mounted for the purpose of testing the chips or for burn in of the chips where the chips are "burnt-in" or conditioned for use.
In the case of ceramic carriers and especially in the case of multi-layer ceramic carriers, the metalization, and especially the metalization between the various layers, fans out from a more dense configuration toward the center of the chip carrier to a less dense configuration toward the outer edges of the ceramic chip carrier. This tends to cause a bulging of the surface of the chip carrier on which the attachment pads are located, this outward bulging being in an essentially convex shape.
In one technique for chip attachment, dendrites are grown on the chip attachment pads on the ceramic substrate, and the chips have solder balls which contact the dendrites and form a releasable or removable connection of the chip to the chip carrier. This dendritic-type connection requires a relatively flat or planar surface, and the curved configuration or curvature of the substrate often prevents good solid connection between the solder balls on the chip and the dendrite connections grown on the pads on the chip carrier. While in some instances during the manufacturing process it may be possible to detect this curvature and take steps, such as grinding the ceramic, nevertheless this procedure is expensive, and the curvature is not always detected. Indeed, in certain rework conditions, the curvature may have gone undetected or, alternatively, the substrates may have been designed to be used with chips in such a way that the curvature had no detrimental effect. However, it is necessary in many instances to deal with the curvature condition on ceramic or other type chip carrier to provide an essentially planar surface on which the dendritic connections are grown and to which the solder balls are connected for testing burn-in or, even in some instances, a connection for a chip in its operating mode.